Administrators of computer networks generally think of network security in terms of abstract security policies. The administrators design the security policies to protect their organization's information resources against threats that may compromise the confidentiality, integrity, or availability of sensitive data. However, the way that people conceptualize security policies does not match the way that they must implement them using conventional, rule-based security policy models.
A computer network generally includes a number of devices, including switches and routers, connected so as to allow communication among the devices. The devices are often categorized into two classes: end stations such as work stations, desktop PCs, printers, servers, hosts, fax machines, and devices that primarily supply or consume information; and network devices such as switches and routers that primarily forward information between the other devices. In this context, the term “administrators” refers to the people who are in charge of interpreting an organization's security policy as it applies to network usage. They are also responsible for writing and applying the security policy. The term “users” refers to people working in the same organization as the administrators and who depend on the network to perform their jobs.
A network security policy defines rules for allowing or disallowing a specific type of network traffic by a specific user or group of users, or a specific end station or group of end stations, under specific conditions. Its purpose is to protect the organization's information resources based on expectations of proper computer and network use. To adequately protect an organization's information assets, an administrator must develop a comprehensive set of security policies that covers all types of network traffic for each user or object at the organization under each set of operational conditions.
The network devices enforce the security policies. The functions of network devices such as switches and routers include receiving packets of data, and determining whether to forward each packet to another device or location, or to refuse to forward a packet. The particular way that these functions operate is determined, in part, by control instructions stored in the network device. However, there has been a lack of efficient way for an administrator to build and manage policies.